Xaml，System.Windows.Controls.DataVisualization.Charting-将X轴标签显示为秒而不是时间？

Question

We collect data from a gyroscope at a variable sampling frequency from 50 Hz to 800 Hz. The Y-Axis values are doubles, the X-Axis values are DateTime values converted from OADate. Currently the chart displays a timestamp (eg 8:00:32 am, 8:00:33 am) on the X-Axis. I've also tried accumulating the periods in a TimeSpan , but the chart creates a label for each sample (of which there are thousands) which causes the X-Axis labels to be unreadable. I would like the X-Axis to display the elapsed duration in seconds instead of a time (eg 0,1,2,3...). How do I do that programmatically?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.DataVisualization.Charting;
using System.Windows.Media;
using System.Windows.Navigation;
using MathNet.Numerics.Data.Text;
using MathNet.Numerics.LinearAlgebra;

public class BlahBlah
{
        private const int REC_NUM = 0;
        private const int DATE = 1;
        private const int X_FIELD = 2;

        private void CreateData(Dictionary<string, Series> dictionary, IEnumerable<Vector<double>> record)
        {
            dictionary.Clear();
            List<Tuple<DateTime, double>> tX = new List<Tuple<DateTime, double>>();

            //Take the first record and perfrom some initialization...
            var firstRecord = record.First();

            long count = 0;
            DateTime last = DateTime.FromOADate(firstRecord[DATE]);
            DateTime current;
            TimeSpan ts = new TimeSpan(0);
            //Now loop through all the records
            foreach (var v in record)
            {
                double dx = 0;

                dx = v[X_FIELD]);

                current = DateTime.FromOADate(v[DATE]);
                ts = ts +  current.Subtract(last);

                //My attempt at using timespan
                //tX.Add(new Tuple<TimeSpan, double>(ts, lx));

                tX.Add(new Tuple<DateTime, double>(DateTime.FromOADate(v[DATE]), dx));
                last = current;
                count++;
            }

            Color cs = (Color)ColorConverter.ConvertFromString("#4FD7DA");

            Style style = new Style();

            style = new Style(typeof(Control));
            style.Setters.Add(new Setter(Control.BackgroundProperty, new SolidColorBrush(cs)));
            //Turn off datapoints by setting the style to null
            style.Setters.Add(new Setter(LineDataPoint.TemplateProperty, null));

            dictionary.Add("x", new LineSeries() {
                Name = "x",
                ItemsSource = tX,
                IndependentValueBinding = new System.Windows.Data.Binding("Item1"),
                DependentValueBinding = new System.Windows.Data.Binding("Item2"),
                Title = "X Axis",
                DataPointStyle = style

            });
        }
    }

...

chart1.Series.Add(dictionary["x"]);

Thanks in advance!

Answer 1

You are right with accumulating the TimeSpan values, but instead of using TimeSpan/DateTime values itself you can use Seconds value of TimeSpan. And change your ItemSource to

List<Tuple<int, double>> tX = new List<Tuple<int, double>>();

If you want to display the elapsed duration in seconds instead of a time (eg 0,1,2,3...), during the build of data you should remember the first DateTime value (0 point), than subtract it from the DateTime of next sample and use the Seconds or TotalSeconds (if there are a thousands samples) of resulting TimeSpan as elapsed seconds value